The chemical modification of surfaces to achieve desired chemical and/or physical characteristics has been previously described. For example, U.S. Pat. Nos. 4,722,906; 4,973,493; 4,979,959; 5,002,582; and 5,512,329 (each of which is commonly owned by the assignee of the invention described herein, and the disclosure of each is incorporated herein by reference), relate to surface modification by the use of latent reactive groups to achieve covalent coupling of reagents such as biomolecules and synthetic polymers to various substrates. The preferred latent reactive group is typically described as a photochemically reactive functional group ("photoreactive species"). When exposed to an appropriate energy source, a photoreactive species undergoes a transformation from an inactive state (i.e., ground state) to a reactive intermediate capable of forming covalent bonds with appropriate materials.
Such latent reactive groups can be used, for instance, to first derivatize a target molecule (e.g., thermochemically), in order to then photochemically attach the derivatized target molecule to a surface. Such a sequential approach is suitable in many situations, but can lack such attributes as speed, versatility, and ease of use, particularly when used with target molecules that are inherently difficult to first derivatize or under conditions that would result in loss of biological activity.
Latent reactive groups can also be used to prepare photoactivatable heterobifunctional molecules as linking agents, e.g., having a photoreactive species at one end or portion with a thermochemically attachment group at another (see, e.g., the above-captioned '582 patent, and U.S. Pat. No. 4,309,453, Reiner et al.). Such linking agents can be used to either attach nonreactive compounds to a surface or to prime a relatively inert surface in order to render it reactive upon exposure to suitable actinic radiation.
U.S. Pat. No. 5,414,075 (commonly owned by the assignee of the present invention and incorporated by reference herein), describes the use of linking agents to prime a surface to provide the surface with photoactivatable groups. This patent describes a restrained, multifunctional reagent useful for priming a support surface, or for simultaneous application with a target molecule to a support. Reagents such as those described above, including those described in the '075 patent, are generally hydrophobic. As a result, they are of relatively low solubility in aqueous systems, thereby often limiting their usefulness in hydrophilic applications.
U.S. Pat. No. 5,714,360, also commonly owned by the present assignee (and also incorporated herein by reference), describes a chemical linking agent comprising a di-or higher functional photoactivatable charged compound. The linking agent provides at least one group that is charged under the conditions of use, in order to provide improved water solubility, and two or more photoactivatable groups in order to allow the agent to be used as a linking agent in aqueous systems. The "Y group" that provides the core radical is defined as a radical containing one or more charged groups, such as the linear and heterocyclic nitrogen-containing (e.g., quaternary ammonium) radicals exemplified therein. In a preferred embodiment, the charged groups include, but are not limited to, salts of organic acids (such as sulfonate, phosphonate, and carboxylate groups), onium compounds (such as quaternary ammonium, sulfonium, and phosphonium groups), and protonated amines, as well as combinations thereof. The photoreactive species can be provided by two or more radicals of an aryl ketone such as benzophenone.
While the reagents of the art are sufficient, if not preferred, for many applications, there remain applications in which various other properties or attributes, such as water solubility, ease of synthesis and/or hemocompatability, are not optimally provided by the reagents of the art.